Basslink Subsea Cable Environmental Impact Revealed

The encrusted iron conduit housing the cable (arrow) is now encrusted with marine organisms.

An independent review committee has published a study on the environmental impact of 290 km-long Basslink subsea power cable.

According to the study led by associate professor John Sherwood of Deakin University, Australia, the Basslink subsea cable impact on the seabed and associated organisms is “transient and minor”.

Using a suite of data that included repeated video surveys of the cable and seabed, the study has come up with the following findings:

Off Victoria, in water depths around 15 meters, the trench and cable were buried by sand and became indistinguishable from the natural seabed within 2 years.

Off the Tasmanian coast, the iron pipe conduit containing the cable became encrusted by marine species similar to those inhabiting the natural reef—that process occurring within 3.5 years.

In deeper parts of the cable route (down to 80 meters water depth), it took 1 to 1.6 years for all traces of the trench/cable to disappear. This change extended over one third of the cable route and resulted from natural sediment infilling the trench.

Direct measurement of the total magnetic field associated with the operating cable showed a variation of <1% of the natural field as measured 5 meters above the cable.

Basslink plays a key role in the distribution of power between the Australian states of Victoria and Tasmania. The cable stretches from George Town in Tasmania to Loy Yang in Victoria.

To remind, Basslink experienced a fault on December 20, 2015, approximately 100 km off the Tasmanian coastline. The cable came back to service on June 10, 2016. Following an investigation, the outage has been described as ‘cause unknown’ by the investigating team.